Positioning reference signal (PRS) generation for multiple transmit antenna systems

ABSTRACT

Disclosed embodiments pertain to a method of generating a Positioning Reference Signal (PRS) sequence for a system comprising a plurality of physical transmitting antenna elements serving a single cell. In some embodiments, the method may comprise: assigning a distinct Physical Antenna Port (PAP) identifier (ID) to a subset of the plurality of physical transmitting antenna elements; and generating PRS sequences for the subset of the plurality of physical transmitting antenna elements, wherein each PRS sequence corresponds to a physical transmitting antenna element in the subset of the plurality of physical transmitting antenna elements, and each PRS sequence has a corresponding frequency shift based, at least in part, on the PAP ID (h) of the corresponding physical transmitting antenna element.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of and priority to U.S. ProvisionalApplication No. 62/160,442 entitled “Positioning Reference Signal (PRS)Generation for Multiple Transmit Antenna Systems,” filed May 12, 2015,which is assigned to the assignee hereof and incorporated by reference,in its entirety, herein.

FIELD

The subject matter disclosed herein relates to Positioning ReferenceSignal (PRS) generation for multiple transmit antenna systems.

BACKGROUND

It is often desirable to know the location of a terminal such as acellular phone. For example, a location services (LCS) client may desireto know the location of a terminal in the case of an emergency servicescall or to provide some service to the user of the terminal such asnavigation assistance or direction finding. The terms “location” and“position” are synonymous and are used interchangeably herein.

In Observed Time Difference of Arrival (OTDOA) based positioning, themobile station may measure time differences in received signals from aplurality of base stations. Because positions of the base stations areknown, the observed time differences may be used to calculate thelocation of the terminal. To further help location determination,Positioning Reference Signals (PRS) are often provided by a base station(BS) in order to improve OTDOA positioning performance. The measuredtime difference of arrival of the PRS from a reference cell (e.g. theserving cell) and one or more neighboring cells is known as theReference Signal Time Difference (RSTD). Using the RSTD measurements,the absolute or relative transmission timing of each cell, and the knownposition(s) of BS physical transmitting antenna element(s) for thereference and neighboring cells, the UE's position may be calculated.

However, when Base Stations (BS) use multiple physical transmittingantenna elements and the physical transmitting antenna elements areswitched between PRS occasions, UE's that utilize multiple PRS occasionsand coherent averaging/integration over the multiple PRS occasions todetermine a Time of Arrival (TOA) value may obtain incorrect resultsbecause different propagation channels may have been used for differentPRS occasions. Similarly, in a conventional distributed antenna system(DAS) spatially separate physical transmitting antenna elements, whichbelong to the same cell and share the same cell Physical Cell Identifier(PCI), transmit the same PRS signal. Consequently, in conventional DAS,the location of the signal transmitter in the DAS case may be ambiguous,and UE position calculation may be erroneous or not be possible.Position calculation is also ambiguous in traditional systems using lowpower Remote Radio Heads (RRHs) or small cells (e.g. femtocells) withina macrocell coverage area because the transmission points created by thespatially separate RRHs or small cells may have the same PCIs as themacro cell and consequently transmit identical PRS signals.

SUMMARY

In some embodiments, a processor-implemented method of generating aPositioning Reference Signal (PRS) sequence may comprise: assigning adistinct Physical Antenna Port (PAP) identifier (ID) to each physicaltransmitting antenna element in a plurality of physical transmittingantenna elements serving a single cell; and generating a plurality ofPRS sequences, each PRS sequence in the plurality of PRS sequencescorresponding to a distinct physical transmitting antenna element in theplurality of physical transmitting antenna elements, wherein each PRSsequence has a corresponding frequency shift based, at least in part, ona corresponding PAP ID (h) of a corresponding physical transmittingantenna element.

In some embodiments, an apparatus may comprise: a transceiver, whereinthe transceiver capable of transmitting PRS information; and a processorcoupled to the transceiver, wherein the processor may be configured to:assign a distinct Physical Antenna Port (PAP) identifier (ID) to eachphysical transmitting antenna element in a plurality of physicaltransmitting antenna elements serving a single cell; and generate aplurality of PRS sequences, each PRS sequence in the plurality of PRSsequences corresponding to a distinct physical transmitting antennaelement in the plurality of physical transmitting antenna elements,wherein each PRS sequence has a corresponding frequency shift based, atleast in part, on a corresponding PAP ID (h) of a corresponding physicaltransmitting antenna element.

In some embodiments, an apparatus may comprise: transceiver meanscapable of transmitting PRS information; and processing means coupled tothe transceiving means, wherein the processing means may comprise: meansfor assigning a distinct Physical Antenna Port (PAP) identifier (ID) toeach physical transmitting antenna element in a plurality of physicaltransmitting antenna elements serving a single cell; and means forgenerating a plurality of PRS sequences, each PRS sequence in theplurality of PRS sequences corresponding to a distinct physicaltransmitting antenna element in the plurality of physical transmittingantenna elements, wherein each PRS sequence has a correspondingfrequency shift based, at least in part, on a corresponding PAP ID (h)of a corresponding physical transmitting antenna element.

In some embodiments, an article may comprise: a non-transitory computerreadable medium comprising instructions to that are executable by aprocessor to: assign a distinct Physical Antenna Port (PAP) identifier(ID) to each physical transmitting antenna element in a plurality ofphysical transmitting antenna elements serving a single cell; andgenerate a plurality of PRS sequences, each PRS sequence in theplurality of PRS sequences corresponding to a distinct physicaltransmitting antenna element in the plurality of physical transmittingantenna elements, wherein each PRS sequence has a correspondingfrequency shift based, at least in part, on a corresponding PAP ID (h)of a corresponding physical transmitting antenna element.

The methods disclosed may be performed by one or more of servers(including location servers), mobile stations, etc. using LPP, LPPe orother protocols. Embodiments disclosed also relate to software,firmware, and program instructions embodied on and/or created, stored,accessed, read or modified by processors using non-transitory computerreadable media or computer readable memory.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A shows an architecture of an exemplary system capable ofproviding Location Services to UEs including the transfer of locationassistance data or location information.

FIG. 1B is a simplified block diagram illustrating the provisionLocation Services to UEs including the transfer of location assistancedata or location information.

FIGS. 2A and 2B illustrate exemplary PRS allocations in an LTE resourceblock for two exemplary system configurations.

FIG. 2C illustrates a resource block showing six distinct diagonalpatterns of PRS symbols.

FIG. 2D illustrates the message flow of a basic procedure that supportstransfer of assistance data from a server to a mobile station, andtransfer of location information from a mobile station to a server.

FIG. 3A shows a traditional single physical transmitting antenna elementsystem with a single physical transmitting antenna element radiating athigh power.

FIG. 3B illustrates exemplary multiple transmit antenna system with fourphysical transmitting antenna elements.

FIG. 4 illustrates an exemplary RRH system with multiple RRHtransmitters serving a single cell.

FIG. 5A shows an exemplary mapping of logical antenna port 6 used forPRS transmission in an antenna switching system to Physical AntennaPorts (PAP) with PAP ID 0 and 1.

FIG. 5B shows an exemplary mapping of logical antenna Port 6 used forPRS transmission in a DAS or RRH system to Physical Antenna Ports PAP0through PAP5 with PAP ID 0 through PAP ID 5, respectively.

FIG. 6A shows a flowchart for an exemplary method to determine theposition of a mobile station in a manner consistent with disclosedembodiments.

FIG. 6B shows a flowchart for an exemplary method to determine theposition of a mobile station in a manner consistent with disclosedembodiments.

FIG. 7A shows a flowchart for an exemplary method to determine theposition of a mobile station in a manner consistent with disclosedembodiments.

FIG. 7B shows a flowchart for an exemplary method that may be usedduring a location estimation procedure in a manner consistent withdisclosed embodiments.

FIG. 7C shows an exemplary method of generating distinct PRS sequencesin a system comprising a plurality of physical transmitting antennaelements.

FIG. 7D shows an exemplary method of generating distinct PRS sequenceswith frequency shifts in a system comprising a plurality of physicaltransmitting antenna elements serving a single cell.

FIG. 8 is a schematic block diagram of a mobile station capable ofreceiving location assistance messages and supporting locationdetermination in a manner consistent with disclosed embodiments.

FIG. 9 is a schematic block diagram illustrating an apparatus such as anexemplary server enabled to support the location determination.

DETAILED DESCRIPTION

Embodiments disclosed pertain to apparatus, systems and methods toimprove position determinations and permit the use of PRS patterns forlocation determination in situations where antenna diversity schemes,DAS, and/or RRH systems are being used. In some embodiments, in a systemcomprising a plurality of physical transmitting antenna elements servinga single cell a distinct Physical Antenna Port (PAP) identifier (ID) maybe assigned to each physical transmitting antenna element in a subset oftwo or more of the plurality of physical transmitting antenna elements.PRS sequences corresponding to each physical transmitting antennaelement in the subset of physical transmitting antenna elements may thenbe generated. Each PRS sequence may correspond to a physicaltransmitting antenna element in the subset of physical transmittingantenna elements. In some embodiments, each PRS sequence may have acorresponding frequency shift based on the PAP ID (h) of thecorresponding physical transmitting antenna element. For example, thefrequency shift may be based on a function ƒ(PAP_(h)) obtained from thePAP ID (h) of the corresponding physical transmitting antenna element.

The use of a distinct PRS sequence for each physical transmittingelement in the subset facilitates resolution of ambiguity related to thelocation of a physical transmitting antenna element. Thus, disclosedembodiments facilitate OTDOA based position using PRS in environmentswith multiple physical transmitting elements, such as systems using DASand/or RRHs and/or small cells. In some embodiments, to facilitateutilization of the above frequency shifted PRS signals by legacy mobilestations, the function ƒ(PAP_(h)) may be set to 0 so that no frequencyshift occurs for at least one of the physical transmitting antennaelements in the subset. In some embodiments, ƒ(PAP_(h)) may be based onidentifier associated with a geographic portion of a cell. Further, insome embodiments, the PAP ID (h) may be transmitted to mobile stationsas part of Observed Time Difference of Arrival (OTDOA) assistanceinformation for the corresponding physical transmitting antenna element.

The terms “mobile station” (MS), “user equipment” (UE) or “target” areused interchangeably herein and may refer to a device such as a cellularor other wireless communication device, personal communication system(PCS) device, personal navigation device (PND), Personal InformationManager (PIM), Personal Digital Assistant (PDA), laptop or othersuitable mobile device which is capable of receiving wirelesscommunication and/or navigation signals. The terms are also intended toinclude devices which communicate with a personal navigation device(PND), such as by short-range wireless, infrared, wireline connection,or other connection—regardless of whether satellite signal reception,assistance data reception, and/or position-related processing occurs atthe device or at the PND.

In addition, the terms UE, MS, “mobile station” or “target” are intendedto include all devices, including wireless and wireline communicationdevices, computers, laptops, etc. which are capable of communicationwith a server, such as via the Internet, WiFi, cellular wirelessnetwork, DSL network, packet cable network or other network, andregardless of whether satellite signal reception, assistance datareception, and/or position-related processing occurs at the device, at aserver, or at another device associated with the network. Any operablecombination of the above are also considered a “mobile station.”

FIG. 1A shows an architecture of a system 100 capable of providingLocation Services to UEs including the transfer of location assistancedata or location information, using messages such as Long Term Evolution(LTE) Positioning Protocol (LPP) or LPP extensions (LPPe) messagesbetween UE 120 and server 150, which, in some instances, may take theform of a location server or another network entity. The transfer of thelocation information may occur at a rate appropriate to both UE 120 andserver 150. The LPP Protocol is well-known and described in variouspublicly available technical specifications from an organization knownas the 3rd Generation Partnership Project (3GPP). LPPe has been definedby the Open Mobile Alliance (OMA) and may be used in combination withLPP such that each combined LPP/LPPe message would be an LPP messagecomprising an embedded LPPe message.

In many instances, a BS may use multiple physical transmitting antennaelements 140. For example, in urban environments, there may often be noclear line-of-sight (LOS) between a transmitter and UE 120 so thatsignals may be reflected along multiple paths before reception. Thesereflections can introduce phase shifts, time delays, attenuations, anddistortions that can destructively interfere with one another at thereceiving terminal.

In some embodiments, system 100 may use antenna diversity schemes,and/or a RRH system or DAS with multiple RRH transmitting elements ormultiple physical transmitting antenna elements 140-1, 140-2, 140-3 and140-4 (sometimes collectively referred to as physical transmittingantenna elements 140) to reduce multipath interference and for otherreasons. For example, system 100 may be a DAS, which is a network ofspatially separated physical transmitting antenna elements 140-1, 140-2,140-3 and 140-4 connected to a common source. The DAS' may replace asingle physical transmitting antenna element radiating at high power ina cell with a group of spatially distributed physical transmittingantenna elements 140-1, 140-2, 140-3 and 140-4 that cover the same cell.The DAS may permit coverage over the same area as a single physicaltransmitting antenna element but with reduced total power and improvedreliability. For example, a single base station and a group of low powerphysical transmitting antenna elements 140-1, 140-2, 140-3 and 140-4 maybe used to provide wireless coverage for an entire building, a cityblock, a campus, or another area.

As another example, system 100 may take the form of a Remote Radio Head(RRH) system or a small cell system where a network of spatiallydistributed radio transmitters, which may be physically remote from aBS, are connected to the BS using fiber optic cables or other high speedlinks. For example, multiple physical transmitting antenna elements 140or RRH transmitting elements or small cell transmitting antenna elementsmay collectively serve a single cell, and RRHs or small cells may beused to extend the coverage of a BS into tunnels, rural areas etc.

For simplicity, only one UE 120 and server 150 are shown in FIG. 1A. Ingeneral, system 100 may comprise multiple cells with additional networks130, LCS clients 160, UEs 120, servers 150, physical transmittingantenna elements 140, and Space Vehicles (SVs) 180. System 100 mayfurther comprise a mix of cells using some combination of a singlephysical transmitting antenna element, antenna diversity schemes, DAS,and/or RRHs or small cells in a manner consistent with embodimentsdisclosed herein.

UE 120 may be capable of wirelessly communicating with server 150through one or more networks 130 that support positioning and locationservices, which may include, but is not limited to, the Secure UserPlane Location (SUPL) location solution defined by OMA and the ControlPlane location solution defined by 3GPP for use with an LTE servingnetwork. For example, Location services (LCS) may be performed on behalfof LCS Client 160 that accesses server 150 (which may take the form of alocation server) and issues a request for the location of UE 120. Server150 may then respond to LCS client 160 with a location estimate for UE120. LCS Client 160 may also be known as a SUPL Agent—e.g. when thelocation solution used by server 150 and UE 120 is SUPL. In someembodiments, UE 120 may also include an LCS Client or a SUPL agent (notshown in FIG. 1A) that may issue a location request to some positioningcapable function within UE 120 and later receive back a locationestimate for UE 120. The LCS Client or SUPL Agent within UE 120 mayperform location services for the user of UE 120—e.g. provide navigationdirections or identify points of interest within the vicinity of UE 120.

Server 150 as used herein may be a SUPL Location Platform (SLP), anevolved Serving Mobile Location Center (eSMLC), a Serving MobileLocation Center (SMLC), a Gateway Mobile Location Center (GMLC), aPosition Determining Entity (PDE), a Standalone SMLC (SAS), and/or thelike.

As illustrated in FIG. 1A, the UE 120 may communicate with server 150through network 130 and physical transmitting antenna elements 140,which may be associated with network 130. UE 120 may receive and measuresignals from physical transmitting antenna elements 140, which may beused for position determination. In some embodiments, some physicaltransmitting antenna elements 140 may form part of a wirelesscommunication network, which may be a wireless wide area network (WWAN).Other physical antenna transmitting elements 140 may form part ofwireless local area network (WLAN), a wireless personal area network(WPAN), and so on. The term “network” and “system” are often usedinterchangeably herein. A WWAN may be a Code Division Multiple Access(CDMA) network, a Time Division Multiple Access (TDMA) network, aFrequency Division Multiple Access (FDMA) network, an OrthogonalFrequency Division Multiple Access (OFDMA) network, a Single-CarrierFrequency Division Multiple Access (SC-FDMA) network, Long TermEvolution (LTE), WiMax and so on.

A CDMA network may implement one or more radio access technologies(RATs) such as cdma2000, High Rate Packet Data (HRPD), Wideband-CDMA(W-CDMA), and so on. Cdma2000 includes IS-95, IS-2000, and IS-856standards. A TDMA network may implement Global System for MobileCommunications (GSM), Digital Advanced Mobile Phone System (D-AMPS), orsome other RAT. GSM, W-CDMA, and LTE are described in documents from3GPP. WCDMA is also part of the Universal Mobile TelecommunicationsSystem (UMTS). HRPD and Cdma2000 are described in documents from aconsortium named “3rd Generation Partnership Project 2” (3GPP2). 3GPPand 3GPP2 documents are publicly available. A WLAN may be an IEEE802.11x network, and a WPAN may be a Bluetooth network, an IEEE 802.15x,or some other type of network. The techniques may also be implemented inconjunction with any combination of WWAN, WLAN and/or WPAN. For example,physical transmitting antenna elements 140 and network 130 may form partof, e.g., an evolved UMTS Terrestrial Radio Access Network (E-UTRAN)(LTE) network, a W-CDMA UTRAN network, a GSM/EDGE Radio Access Network(GERAN), a 1×RTT network, an Evolution-Data Optimized (EvDO) network, aWiMax network or a WLAN.

UE 120 may also receive signals from one or more Earth orbiting SpaceVehicles (SVs) 180-1 or 180-2 collectively referred to as SVs 180, whichmay be part of a satellite positioning system (SPS). SVs 180, forexample, may be in a constellation of Global Navigation Satellite System(GNSS) such as the US Global Positioning System (GPS), the EuropeanGalileo system, the Russian Glonass system or the Chinese Compass/BeiDousystem. In accordance with certain aspects, the techniques presentedherein are not restricted to global systems (e.g., GNSS) for SPS. Forexample, the techniques provided herein may be applied to or otherwiseenabled for use in various regional systems, such as, e.g., Quasi-ZenithSatellite System (QZSS) over Japan, Indian Regional NavigationalSatellite System (IRNSS) over India, and/or various augmentation systems(e.g., an Satellite Based Augmentation System (SBAS)) that may beassociated with or otherwise enabled for use with one or more globaland/or regional navigation satellite systems. By way of example but notlimitation, an SBAS may include an augmentation system(s) that providesintegrity information, differential corrections, etc., such as, e.g.,Wide Area Augmentation System (WAAS), European Geostationary NavigationOverlay Service (EGNOS), Multi-functional Satellite Augmentation System(MSAS), GPS Aided Geo Augmented Navigation or GPS and Geo AugmentedNavigation system (GAGAN), and/or the like. Thus, as used herein an SPSmay include any combination of one or more global and/or regionalnavigation satellite systems and/or augmentation systems, and SPSsignals may include SPS, SPS-like, and/or other signals associated withsuch one or more SPS.

FIG. 1B shows a simplified block diagram illustrating some entities in asystem 175 capable of determining the location of UE 120. Referring toFIG. 1B, UE 120 may measure signals from reference source(s) 170 toobtain measurements and/or location estimate 173. Reference source(s)170 may represent signals from SVs 180 and/or physical transmittingantenna elements 140 associated with network 130. Accordingly, UE 120may obtain measurements 172 by measuring pseudo-range measurements forSVs 180 and/or OTDOA related measurements from physical transmittingantenna elements 140. In some instances, UE 120 may also obtain alocation estimate 173 by using measurements 172, which may bepseudo-range and/or OTDOA related measurements to derive an estimatedposition for UE 120. UE 120 may provide location related information,such as location estimate 173 or measurements 172 (e.g., satellitemeasurements from one or more GNSSs, or network measurements such asRSTDs from one or more networks, etc.) to server 150.

In some instances, the OTDOA related measurements taken by UE 120 may besent to server 150 to derive a position estimate for UE 120. Server 150may provide location related information, such as an approximatelocation of UE 120 and/or location assistance data 178 to UE 120, whichmay be used to assist UE 120 in acquiring and measuring signals from SVs180 and physical transmitting antenna elements 140, and/or in derivingor refining a location estimate 173 from these measurements 172. Forexample, UE 120, which in some instances may take the form of a SecureUser Plane (SUPL) Enabled Terminal (SET), may communicate with server150 and use location assistance data 178 obtain a location estimate forUE 120, which may then be communicated to LCS client 160 (not shown inFIG. 1B).

Referring to FIG. 1A, in some embodiments, physical transmitting antennaelements 140 may also transmit Positioning Reference Signals (PRS). PRS,which have been defined in 3GPP Long Term Evolution (LTE) Release-9, aretransmitted by a base station in special positioning subframes that aregrouped into positioning occasions. For example, in LTE, the positioningoccasion, which can comprise 1, 2, 4, or 6 consecutive positioningsubframes, occurs periodically at 160, 320, 640, or 1280 millisecondintervals.

Within each positioning occasion, PRSs are transmitted with a constantpower. PRS can also be transmitted with zero power (i.e., muted).Muting, which turns off a regularly scheduled PRS transmission, may beuseful when PRS patterns between cells overlap. Muting aids signalacquisition by UE 120. Muting may be viewed as the non-transmission of aPRS for a given positioning occasion in a particular cell. Mutingpatterns may be signaled to UE 120 using bitstrings. For example, in abitstring signaling a muting pattern, if a bit at position j is set to“1”, then an UE may infer that the PRS is muted for the j^(th)positioning occasion.

Muting may, in some instances, facilitate separation of transmissionpoints in the time domain. However, when muting is used for locationdetermination, mobile stations typically report the muting pattern andRSTD measurements to a location server, which creates additionaloverhead. Moreover, in addition to the overhead above, to avail oflocation services based on muting pattern measurements, a mobile stationmay request further location assistance, to determine: (i) when themuting patterns are associated with location services (so that themuting pattern measurements associated with location services may bereported); and (ii) when they are being used solely for interferencemitigation (so that the muting pattern measurements related tointerference mitigation are not reported).

Moreover, legacy mobile stations without the capacity to measure themuting pattern may be unable to avail of location services. For example,legacy mobile stations may merely measure a “composite signal” and alocation server may be unable to identify the transmission point basedon the measurements. In addition, because muting patterns are primarilydesigned to reduce interference, the use of muting patterns toadditionally distinguish transmission points (e.g. create RRHseparation) may lead to network complexities and further constrain theuse of muting patterns for interference reduction. Further, 16-bitmuting patterns do not permit separation of the up to 72 transmissionpoints supported under the LPP standard.

To further improve hearability of PRS, positioning subframes may below-interference subframes that are transmitted without user datachannels. As a result, in ideally synchronized networks, PRSs mayreceive interference from other cell PRS' with the same PRS patternindex (i.e., with the same frequency shift), but not from datatransmissions. The frequency shift is defined as a function of thePhysical Cell Identifier (PCI) resulting in an effective frequencyre-use factor of 6.

FIGS. 2A and 2B illustrate exemplary PRS allocations in an LTE resourceblock for two exemplary system configurations. LTE supports thetransmission of reference signals using one, two or four PhysicalBroadcast Channel (PBCH) antenna ports. FIG. 2A shows the configurationfor a system 200 with one and two PBCH antenna ports. FIG. 2B shows theconfiguration for a system 220 with four PBCH antenna ports. In FIGS. 2Aand 2B time is shown along the horizontal axis and frequency on thevertical axis. As shown in FIGS. 2A and 2B, LTE PRS' are transmitted onlogical antenna port 6.

For LTE Radio Frames of 10 ms duration each in downlink FrequencyDivision Duplex (FDD) mode, the LTE Radio Frames may be organized intoten subframes of 1 ms duration each. In the frequency domain, theavailable bandwidth may be divided into uniformly spaced orthogonalsubcarriers. For example, for a normal length cyclic prefix using 15 KHzspacing, subcarriers may be bracketed into a group of 12. Each grouping,which may comprise 12 subcarriers, is termed a resource block.

When a normal cyclic prefix (CP) is assumed, the resource block mayinclude 14 Orthogonal Frequency Division Multiplexing (OFDM) symbols intime and 12 subcarriers in frequency. In FIGS. 2A and 2B above, eachsubcarrier occupies 15 kHz and the OFDM symbol duration including thecyclic prefix is 1/14 milliseconds (UE). The number of availableresource blocks on each channel, which is also called the transmissionbandwidth configuration of an LTE carrier, may be in the range from 6 to100 resource blocks, corresponding to channel bandwidths of 1.4 MHz to20 MHz.

In FIGS. 2A and 2B, each square indicates a resource element for asubcarrier with time domain index “l”. Further, in FIGS. 2A and 2B, OFDMsymbols that have been labeled R₆ are PRS symbols, such as, for example,PRS symbols 202 (FIG. 2A) and 222 (FIG. 2B). Thus, the squares labeledR₆ indicate PRS resource elements in a block of 12 subcarriers over 14OFDM symbols.

As shown in FIGS. 2A and 2B, the PRS symbols are arranged in a diagonalpattern. In frequency domain, the PRS symbols are 6 subcarriers apart asshown by PRS symbols 202 and 204 in FIG. 2A, and PRS symbols 222 and 224in FIG. 2B.

FIG. 2C illustrates a resource block showing six distinct diagonalpatterns of PRS symbols. The PRS symbols are shown in FIG. 2C as CID#0225, CID#1 227, CID#2 229, CID#3 231, CID#4 233, CID#5 235, and CID #5235. In FIG. 2C, each PRS symbol is represented using a distinct shadingpattern. The PRS pattern is determined by the frequency shift, which isdefined as a function of the Physical Cell Identifier (PCI) resulting inan effective frequency re-use factor of 6. The frequency shift is givenby vshift=mod(PCI, 6), where the “mod” function represents the modulusand yields the remainder when the first argument (PCI) is divided by thesecond argument (6). Thus, the PCI for a cell effectively determines oneof six available PRS patterns. If two cells have the same vshift value,for example cells with PCI's 0 and 6, those cells will collide in thefrequency domain and interfere with each other.

The PRS sequence transmitted by a cell is specified in 3GPP standardsand technical specifications as follows:

$\begin{matrix}{{{r_{l,n_{s}}(m)} = {{\frac{1}{\sqrt{2}}\left( {1 - {2 \cdot {c\left( {2\; m} \right)}}} \right)} + {j\frac{1}{\sqrt{2}}\left( {1 - {2 \cdot {c\left( {{2\; m} + 1} \right)}}} \right)}}},{m = 0},1,{{\ldots\mspace{14mu} 2N_{R\; B}^{{m\; a\; x},{D\; L}}} - 1}} & (1)\end{matrix}$where,

-   n_(s) is the slot number within a radio frame (slot=0.5 UE; frame=10    UE), n_(s)=0 . . . 19;-   l is the OFDM symbol number within the slot;

l=0 . . . 6 for normal cyclic prefix; and

l=0 . . . 5 for extended cyclic prefix.

-   c(i) is a length-31 Gold sequence-   N_(RB) ^(max, DL) is the largest downlink bandwidth configuration,    expressed in multiples of N_(SC) ^(RB);-   N_(sc) ^(RB) is the resource block size in the frequency domain,    expressed as a number of subcarriers.

N_(sc) ^(RB)=12 subcarriers for PRS, with 15 kHz spacing (180 kHztotal).

A Gold sequence is a binary sequence used in telecommunication andsatellite navigation and is useful when multiple devices arebroadcasting in the same frequency range because a set of Gold codesequences have small bounded cross-correlations.

The pseudo-random sequence generator for c(i) is initialized withc _(init)=2¹⁰·(7·(n _(s)+1)+l+1)·(2·N _(ID) ^(cell)+1)+2·N _(ID) ^(cell)+N _(CP)  (2)at the start of each OFDM symbol where

$N_{C\; P} = \left\{ \begin{matrix}1 & {{for}\mspace{14mu}{normal}\mspace{14mu}{Cyclic}\mspace{14mu}{Prefix}} \\0 & {{for}\mspace{14mu}{extended}\mspace{14mu}{Cyclic}\mspace{14mu}{Prefix}}\end{matrix} \right.$

N_(ID) ^(cell) Physical layer Cell Identity (PCI).

The reference signal sequence is mapped to complex-valued QPSKmodulation a_(k,l) ^((p)) symbols used as reference signal for antennaport p=6 in slot n_(s):a _(k,l) ^((p)) =r _(l,n) _(s) (m′)where,

Normal cyclic prefix:

-   -   k=6(m+N_(RB) ^(DL)−N_(RB) ^(PRS))+(6−l+v_(shift))mod 6

$l = \left\{ \begin{matrix}{3,5,6} & {{{if}\mspace{14mu} n_{s}{mod}\mspace{14mu} 2} = 0} \\{1,2,3,5,6} & {{{if}\mspace{14mu} n_{s}{mod}\mspace{14mu} 2} = {1\mspace{14mu}{and}\mspace{14mu}\left( {1\mspace{14mu}{or}\mspace{14mu} 2\mspace{14mu}{PBCH}\mspace{14mu}{antenna}\mspace{14mu}{ports}} \right)}} \\{2,3,5,6} & {{{if}\mspace{14mu} n_{s}{mod}\mspace{14mu} 2} = {1\mspace{14mu}{and}\mspace{14mu}\left( {4\mspace{14mu}{PBCH}\mspace{14mu}{antenna}\mspace{14mu}{ports}} \right)}}\end{matrix} \right.$

-   -   m=0, 1, . . . , 2·N_(RB) ^(PRS)−1    -   m′=m+N_(RB) ^(max,DL)−N_(RB) ^(PRS)

Extended cyclic prefix:

-   -   k=6(m+N_(RB) ^(DL)−N_(RB) ^(PRS))+(5−l+v_(shift)) mod 6

$l = \left\{ \begin{matrix}{4,5,} & {{{if}\mspace{14mu} n_{s}{mod}\mspace{14mu} 2} = 0} \\{1,2,4,5} & {{{if}\mspace{14mu} n_{s}{mod}\mspace{14mu} 2} = {1\mspace{14mu}{and}\mspace{14mu}\left( {1\mspace{14mu}{or}\mspace{14mu} 2\mspace{14mu}{PBCH}\mspace{14mu}{antenna}\mspace{14mu}{ports}} \right)}} \\{2,4,5} & {{{if}\mspace{14mu} n_{s}{mod}\mspace{14mu} 2} = {1\mspace{14mu}{and}\mspace{14mu}\left( {4\mspace{14mu}{PBCH}\mspace{14mu}{antenna}\mspace{14mu}{ports}} \right)}}\end{matrix} \right.$

-   -   m=0, 1, . . . , 2·N_(RB) ^(PRS)−1    -   m′=m+N_(RB) ^(max,DL)−N_(RB) ^(PRS)

The bandwidth for positioning reference signals is N_(RB) ^(PRS) and thecell-specific frequency shift is given by v_(shift)=N_(ID) ^(cell) mod 6(also written as vshift=mod(PCI, 6)). Therefore, the PRS transmitted bya cell is determined by the frame and slot timing of the cell (n_(s),l), the cyclic prefix length (N_(CP)), and the PCI N_(ID) ^(cell).

PRS configuration parameters, such as the number of consecutivepositioning subframes, periodicity, muting pattern, etc. may be decidedby network 130 and may be signaled to UE 120 (e.g. by server 150) aspart of the OTDOA assistance data. OTDOA assistance data may includereference cell information (PCI) and neighbor cell lists containing thePCI of neighbor cells and the PRS configuration parameters for thecells. OTDOA assistance information may allow a UE to determine when aPRS positioning occasion occurs on signals received from various cells,and to determine the PRS sequence transmitted from various cells tomeasure a TOA.

In conventional systems, antenna diversity is often used to mitigatemultipath interference because each physical transmitting antennaelement may experience a different interference environment therebyoffering UE 120 several observations of the same signal. For example, ifone physical transmitting antenna element is experiencing a deep fade,it is likely that another has a sufficient signal at the terminal.However, in conventional systems, the PRSs are transmitted from a singleantenna port—port 6—and therefore, cannot exploit the diversity frommultiple physical transmitting antenna elements. To overcome thislimitation, in conventional systems, base stations may employ switchingof physical transmit antenna elements for the PRS, where the physicaltransmitting antenna element is switched between PRS occasions.Accordingly, each PRS occasion may be transmitted from a single physicaltransmitting antenna element, but PRS occasions alternate betweenseveral physical transmitting antenna elements. In the above situation,if a UE uses multiple PRS occasions and coherent averaging/integrationover the multiple PRS occasions to determine a Time of Arrival (TOA)value, then the TOA value obtained from coherent averaging would beincorrect because of the use of different propagation channels fordifferent PRS occasions.

Similarly, in conventional systems using a DAS, UEs cannot correlatereceived PRS signals with individual DAS elements because geographicallydistributed DAS physical transmitting antenna elements, which belong tothe same cell and share the same cell Physical Cell Identifier (PCI),transmit the same PRS signal. Consequently, the location of the signaltransmitter in the DAS case may be ambiguous, and UE positioncalculation may not be possible.

Position calculation is also ambiguous in traditional systems using lowpower Remote Radio Heads (RRHs) or small cells within a macrocellcoverage area because the transmission points created by the RRHs orsmall cells may have the same PCIs as the macro cell and consequentlytransmit identical PRS signals. For example, this may occur in somescenarios when using LTE-Advanced Cooperative Multi Point (CoMP)transmission. CoMP relates to protocols and techniques for coordinationbetween multiple transmission points to mitigate interference betweentransmitted signals and enhance received signal quality.

In these scenarios, UEs will not be able to correlate received PRSsignals with individual RRH elements thereby creating ambiguity inlocation calculation.

Accordingly, in some embodiments, for example, in situations whereantenna switching is used, OTDOA assistance information may include PRSassistance information, such as antenna switching assistance informationindicating whether antenna switching for PRS transmission is used in acell. In some embodiments, PRS assistance data sent to UE 120 may alsoinclude additional antenna switching assistance information. Forexample, server 150 may include antenna switching assistance informationin OTDOA assistance data provided as part of the LPP or LPPe protocol.

In one embodiment, the antenna switching assistance information mayinclude a Boolean parameter which indicates whether antenna switchingbetween PRS positioning occasions occurs in a cell. The Booleanparameter for a cell may be set to TRUE, if antenna switching occurs inthe cell, or to FALSE, if antenna switching does not occur in the cell.If set to TRUE for a cell, the Boolean parameter may indicate to UE 120that coherent averaging over multiple PRS occasions should not be usedfor that cell. If set to FALSE for a cell, the Boolean parameter mayindicate that UE 120 could use multiple PRS occasions coherently todetermine a TOA value for location determination.

In another embodiment, UE 120 may use a single PRS positioning occasionto determine a time-of-arrival (TOA). If antenna switching assistancedata indicates that antenna switching is used between PRS occasions, UE120 may determine multiple TOA values, for example, by determining oneTOA value every PRS occasion. In case of antenna switching, each TOAfrom a PRS positioning occasion may be slightly different because eachPRS occasion may experience a different interference/channelenvironment. The UE may select the shortest TOA value among the set ofTOA values as a final TOA measurement, since the shortest TOA value maybe closer to the desired LOS delay for position calculation purposes.

If antenna switching assistance data indicates that antenna switching isnot used between PRS occasions, DE 120 may not determine a set of TOAvalues as described above. If PRS are transmitted from a single physicaltransmitting antenna element (e.g., without physical transmittingantenna element switching), each PRS occasion may experience essentiallythe same radio channel, and therefore, determining multiple TOAs may beof no advantage. Accordingly, in some embodiments, UE 120 may useantenna switching assistance data advantageously to decide whether thedetermination of multiple TOA values would be useful, thereby conservingpower and processor resources in situations where antenna switching isnot used.

In another embodiment, the antenna switching assistance information mayprovide antenna switching pattern information. Antenna switching patterninformation may be useful, for example, in situations where antennaswitching is not performed for each PRS positioning occasion, butswitching between physical transmitting antenna elements 140-1, 140-2,140-3, and/or 140-4 may occur every r^(th) PRS positioning occasion,where r≧1, is some integer. For example, for r=2, switching amongphysical transmitting antenna elements 140-1, 140-2, 140-3, and/or 140-4may occur every second PRS positioning occasion.

In some embodiments, antenna switching pattern information may take theform of a bit string. The bit string could indicate, for example, whenantenna switching occurs and how many PRS positioning occasions aretransmitted before a physical transmitting antenna element is switchedin the cell. In some embodiments, antenna switching pattern informationmay be provided using a matrix where each row of the matrix represents aphysical transmitting antenna element, such as one of antennas 140-1,140-2, 140-3, and 140-4, and each column represent a PRS positioningoccasion. Accordingly, for example, a “1” at location (x, y) on thex^(th) row and y^(th) column of the matrix may indicate that a scheduledy^(th) PRS positioning occasion is transmitted by the x^(th) physicaltransmitting antenna element, while a “0” at location (x, y) mayindicate that the scheduled y^(th) positioning occasion PRS occasion isnot transmitted by the x^(th) physical transmitting antenna element. Insome embodiments, switching information could be defined relative to aradio frame with System Frame Number 0 (SFN=0).

For example, in an instance with two physical transmitting antennaelements, antenna switching every PRS positioning occasion could beindicated by:

${{Antenna}\mspace{14mu}{Switching}\mspace{14mu}{Pattern}} = \begin{bmatrix}0 & 1 \\1 & 0\end{bmatrix}$In the above example, each row of the matrix may correspond to aphysical transmitting antenna element and each column of the matrix mayindicate a PRS occasion. In the example above, switching occurs everyPRS positioning occasion.

A matrix to indicate antenna switching every second PRS positioningoccasion may take the form

${{Antenna}\mspace{14mu}{Switching}\mspace{14mu}{Pattern}} = \begin{bmatrix}0 & 0 & 1 & 1 \\1 & 1 & 0 & 0\end{bmatrix}$The matrix above may indicate that physical transmitting antenna element140-1 transmits PRS positioning information for the second two PRSpositioning occasions, while physical transmitting antenna element 140-2transmits PRS positioning information for the first two PRS positioningoccasions. Referring to FIG. 3B, for DAS 350, with physical transmittingantenna elements 140-1, 140-2, 140-3, and 140-4 a matrix to indicateswitching every second PRS positioning occasion may take the form

${{Antenna}\mspace{14mu}{Switching}\mspace{14mu}{Pattern}} = \begin{bmatrix}0 & 0 & 1 & 1 & 0 & 0 & 0 & 0 \\1 & 1 & 0 & 0 & 0 & 0 & 0 & 0 \\0 & 0 & 0 & 0 & 1 & 1 & 0 & 0 \\0 & 0 & 0 & 0 & 0 & 0 & 1 & 1\end{bmatrix}$The matrix above indicates that physical transmitting antenna element140-2 transmits for the first two PRS positioning occasions, followed byphysical transmitting antenna element 140-1, which transmits for thenext two PRS positioning occasions, followed in turn by physicaltransmitting antenna element 140-3 for the two subsequent PRSpositioning occasions, which is then followed by physical transmittingantenna element 140-4 for the next two PRS positioning occasions. Notethat the use of matrices to specify antenna switching patterns isexemplary and for descriptive purposes only and various otherrepresentations are envisaged as would be apparent to one of ordinaryskill in the art.

The 3GPP standard and technical specifications also define logicalantenna ports for the downlink to UE 120. An “antenna port” or a“logical antenna port” is generally used as a generic term for signaltransmission under identical channel conditions. Antenna ports arelogical entities that are dynamically mapped to physical transmittingantenna elements 140 or to Physical Antenna Ports (PAPs). Logicalantenna ports may be viewed as logical channels that are characterizedby the information they transfer, whereas, physical transmitting antennaelements may be viewed as transport channels characterized by how theinformation is transferred. The dynamic mapping of logical antenna portsto physical transmitting antenna elements thus maps logical channels totransport channels by assigning logical antenna ports to physicaltransmitting antenna elements.

Physical Antenna Ports (PAPs) may also identify a portion of a cell. Forexample, physical transmit antenna 140-1 may serve a portion of a cell.If a target device is known to be connected to physical transmit antenna140-1, the location of the target device may be determined at least inpart based on the cell portion associated with the coverage area ofphysical transmit antenna 140-1.

For each LTE operating/transmission mode in the downlink direction forwhich an independent channel is assumed (e.g. Single Input and SingleOutput (SISO) vs. Multiple In Multiple Out (MIMO)), a separate logicalantenna port is defined. LTE symbols that are transmitted via identicallogical antenna ports are subject to the same channel conditions. Themapping of logical antenna ports to physical transmitting antennaelements of a BS may depend on BS implementation.

In some embodiments, for example, where physical transmitting antennaelements 140 represent a DAS with antennas 140-1, 140-2, 140-3 and140-4, logical antenna port 6, which is used for PRS transmission, maybe mapped to Physical Antenna Ports (PAPs), and a PRS sequence may begenerated as a function of the Physical Antenna Port Identifier (PAPID). In equations (3) and (4) below the function of PAP ID is denoted byƒ(PAP_(h)). Similarly, in situations where a cell is served by multipleRRHs or small cells, logical antenna port 6 on the RRHs or small cellsmay be mapped to PAPs, and a PRS sequence may be generated as a functionof the PAP ID. For example, in one implementation, in order todistinguish PRSs at different physical transmitting antenna elements fora particular eNodeB (BS) with PCI N_(ID) ^(cell), the initializationseed for the PRS sequence may be a function of the PAP. Accordingly, insome embodiments, c_(init), in initialization equation (2), above, maybe modified for a PAP as,c _(init)=2¹⁰·(7·(n _(s)+1)+l+1)·(2·N _(ID) ^(cell)+1)+2·N _(ID) ^(cell)+N _(CP)+ƒ(PAP_(h))  (3)where PAP_(h) corresponds to physical antenna port h, for 0≦h≦ρ_(pap),and ρ_(pap) is the number of physical antenna ports. Because c_(init) inEquation (3) above is a function of PAP ID PAP_(h), in some embodiments,a different PRS sequence may be transmitted from each DAS physicaltransmitting antenna element or RRH or small cell.

In another embodiment, c_(init), in initialization equation (2), above,may be modified for a PAP as,c _(init)=2¹⁰·(7·(n _(s)+1)+l+1)·(2·(N _(ID) ^(cell)+ƒ(PAP_(h)))+1)+2·(N_(ID) ^(cell)+ƒ(PAP_(h)))+N _(CP)  (4)ƒ(PAP_(h)) in equations (3) and (4) may be absent or zero for the macrocell. Therefore, according to equations (3) and (4) above, the PRSsequence depends on both the PCI N_(ID) ^(cell), and on the RRH ortransmission point ID ƒ(PAP_(h)).

ƒ(PAP_(h)) may be an integer starting at zero, or, as another example,may start with an offset of 503. In LTE, the PCI can take values from 0through 503, therefore, in some embodiments, new “effective PCIs” givenby ƒ(PAP_(h)) with values greater than 503 may be used for the RRH/DASelements, or in general for the PRS physical transmitting antennaelements.

In some embodiments, ƒ(PAP_(h)) may be based on, obtained from, or equalto, the “Cell Portion ID” defined in 3GPP Technical Specification 36.455“LTE Positioning Protocol A (LPPa)”, Release-12. A Cell Portion is ageographical part of a cell and may be uniquely identified by acorresponding “Cell Portion ID”.

In some embodiments, the frequency shift vshift of the PRS pattern forthe PRS transmission antenna elements, such as for a RRH or DAS element,may be modified based on the sum of the PCI and ƒ(PAPh) as outlined inequation (5) below.vshift=mod((N _(ID) ^(cell)+ƒ(PAP_(h))),6)  (5)When vshift is modified as in Equation (5), the transmission points maybe separated in both, the code- and frequency domain, because eachphysical transmission antenna element associated with a transmissionpoint transmits a different diagonal PRS pattern relative to otherphysical transmitting antenna elements associated with that transmissionpoint. The diagonal pattern transmitted by the physical transmittingantenna element is based on both the PCI associated with thetransmission point and a function ƒ(PAP_(h)) of the PAP ID of thephysical transmitting antenna element.

In some embodiments, server 150 may transmit the PAP ID as part of OTDOAassistance information by server 150. Further, the PAP ID may betransmitted as part of OTDOA assistance information based, in part, onreceived information indicating a capability to generate a replica PRSsequence at UE 120 in communication with server 150. In someembodiments, the OTDOA assistance information may be provided by addingPAP ID, ƒ(PAP_(h)), or information obtained from PAP ID, or a similarfield to appropriate OTDOA assistance information.

In some embodiments, UE 120 may transmit the PAP ID as part of the OTDOAmeasurement information to server 150 in a measurement report message,indicating to server 150 from which PAP the OTDOA measurement has beenmade.

In some embodiments, equations (3) or (4) may be used with antennadiversity schemes because antenna switching may be considered asequivalent to mapping the antennas to PAPs and applying a muting patternfor each physical transmitting antenna element where PRS occasions aremuted alternately between the physical transmitting antenna elements. Insome embodiments, the logical antenna port 6 may be mapped to multiplePAPs based on the number of physical transmitting antenna elementsswitched. For example, in the case of two physical transmitting antennaelements, logical antenna port 6 may be assigned to two PAPs, PAP₀ andPAP₁. According to equations (3) or (4) above, PAP₀ and PAP₁ wouldtransmit a different PRS sequence. Further, in the example above, insome embodiments, antenna switching may be indicated using a mutingpattern defined in the OTDOA assistance data, to indicate that one PAPis muted during PRS transmissions of the other PAP.

In some embodiments, the logical antenna port 6 may be mapped tomultiple PAPs based on the number of physical transmitting antennaelements switched. For example, in the case of two physical transmittingantenna elements, logical antenna port 6 may be assigned to two PAPs,PAP₀ and PAP₁. The frequency shift of the PRS pattern may depend on thePAP ID as described above in equation (5), where vshift=mod((N_(ID)^(cell)+ƒ(PAP_(h))), 6), with ƒ(PAP_(h))=PAP₀ or PAP₁ in the case of twophysical transmitting antenna elements. Therefore, the physicaltransmitting antenna elements identified by PAP₀ and PAP₁ would eachtransmit distinct PRS frequency patterns.

In some embodiments, where different PRS sequences are transmitted (asdescribed above) by different PAPs each associated with a physicaltransmitting antenna element at a different location (e.g. as for a cellwith multiple RRHs), additional OTDOA assistance data may be provided toUE 120 to assist acquisition and measurement of each PRS sequence. As anexample, the approximate expected RSTD for each PRS sequence may beprovided and/or the location or relative location of each of physicaltransmitting antenna elements 140.

In addition, in some embodiments, to ensure that legacy mobile stationsare not affected by the above PRS related changes, mobile stationcapability indication for PAPs may be added to the OTDOA capabilitiesdefined in LPP or LPPe. In one embodiment, for example, to ensure legacysupport, one physical transmitting antenna element, such physicaltransmitting antenna element 140-1 with PAP ID PAP₀, may not change itsPRS sequence or frequency shift pattern, which may be achieved bysetting ƒ(PAP_(h))=0, for h=0, in equations (3) or (4). Similarly,ƒ(PAP_(h)) may be set to 0, for h=0 in equation (5), which relates tothe frequency shift vshift. Accordingly, in the previous example, thePRS sequence and frequency pattern may be unchanged for PAP₀, therebyproviding support for legacy mobile stations.

In some embodiments, where mobile station capability information from UE120 indicates support for multi-PRS sequences and multi-PRS frequencyshifts (i.e., multiple PRS sequences and frequency shifts for a singlePCI) from the same cell/PCI, server 150 may include such cells in OTDOAassistance data and UE 120 may undertake OTDOA measurements fromtransmitters in a DAS or RRH system or small cell system, since physicaltransmitter locations may be mapped to the multi-PRS sequence andfrequency shift.

If mobile station capability information from UE 120 indicates a lack ofsupport for multi-PRS sequences from the same cell/PCI, server 150, maynot include such cells in OTDOA assistance data. As outlined earlier,because OTDOA positioning would be impractical for legacy mobilestations in cells with DAS or RRHs, such cells may already be omittedfrom OTDOA assistance information provided by server 150. Accordingly,the omission of multi-PRS cells from OTDOA assistance data may haveminimal or no impact for legacy mobile stations.

In some embodiments, UE 120 may use the PCI, in conjunction withmulti-PRS sequences and frequency shifts and/or OTDOA assistance datacomprising one or more of: PRS assistance information, antenna switchingassistance information, antenna switching pattern information, and/ormuting information to make OTDOA measurements. In some embodiments, UE120 may make OTDOA measurements using the above information in cellswith antenna diversity, DAS, or RRH systems.

In some embodiments, the OTDOA measurements may be used by UE 120 and/orserver 150 to determine the location of UE 120. For OTDOA positioning,by unambiguously identifying cells, physical transmitting antennaelements 140, or RRHs from which the OTDOA measurements have been made,UE 120 or server 150 may use the actual location of physicaltransmitting antenna elements 140, which can then be utilized forposition calculation.

FIG. 2D illustrates the message flow of a basic procedure that supportstransfer of assistance data from the server 150 to the UE 120 andtransfer of location information (e.g., RSTD measurement) from UE 120 toserver 150 using a connection and, where applicable, a location sessionbetween the UE 120 and server 150 that remains established during theentire data transfer. For the sake of example, the message flow isdescribed as LPP/LPPe positioning protocol messages, but it should beunderstood that other types of messages may be used if desired (e.g. LPPmessages).

In block 21, if the LPP/LPPe capabilities including the multi-PRSsequence and frequency shift and antenna switching assistance datacapabilities of the UE 120 are not known to server 150, then, in someembodiments, server 150 may send an LPP/LPPe Request Capabilitiesmessage to UE 120. The Request Capabilities message, which requests theLPP/LPPe capabilities of the UE 120, may include, among otherparameters, a request for OTDOA capabilities, including capabilityindication for PAPs and/or support for multi-PRS sequences and frequencyshifts from the same cell/PCI.

The UE 120 may respond with a LPP/LPPe Provide Capabilities message sentto the server 150 in block 22 of the message flow. In certain aspects ofthe described embodiments, the Provide Capabilities message may beprovided by UE 120 unsolicited in block 22 in the absence of a RequestCapabilities message being sent in block 21. In another embodiment, theProvide Capabilities message in block 22 may be sent instead by UE 120in association with a request for assistance data sent later in block24. The Provide Capabilities message includes, among other parameters,an indication of UE OTDOA capabilities, including capability indicationfor PAPs and/or support for multi-PRS sequences and frequency shiftsfrom the same cell/PCI.

Actions similar to those performed in blocks 21 and 22 but with messagetransfer in the opposite direction may be performed instead of block 21and 22 or in addition to blocks 21 and 22 to transfer the LPP/LPPecapabilities of server 150 to UE 120 regarding support for OTDOAcapabilities, including capability indication for PAPs and/or supportfor multi-PRS sequences and frequency shifts from the same cell/PCI. Theabove actions are not shown in FIG. 2 and, if used, may make use of areversed LPPe mode whereby a UE 120 is enabled to request and receivecapabilities from a server 150.

In block 23 of the message flow, the server 150 requests locationinformation from UE 120 in a LPP/LPPe Request Location Informationmessage. The request for location information may include a request forRSTD measurements to be performed by UE 120.

In some embodiments, UE 120 may request OTDOA assistance data in orderto fulfill the request received in block 23 and may send an LPP/LPPerequest for assistance data to the server 150, in block 24. In someembodiments, UE 120 may specify the particular assistance datarequested, such as OTDOA assistance data, including one or more of PRSassistance information, antenna switching assistance information,antenna switching pattern information, and/or muting information, and/orPAP assistance information. In some embodiments, block 24 may not occurand the server 150 may decide to send assistance data to UE 120unsolicited. In some embodiments, PAP assistance information may bebased on, obtained from, or equal to ƒ(PAP_(h)).

In block 25 of the message flow, server 150 may obtain the assistancedata to be transferred to UE 120. If block 24 was performed, theassistance data may comprise all of the assistance information requestedby the UE 120 that may be available to server 150. The assistance datatransferred in block 25 may include the OTDOA assistance data defined inLPP/LPPe and may also include antenna switching and PAP assistanceinformation.

The UE 120 may then measure RSTDs between a reference cell and multipleneighbor cells based on the OTDOA assistance data received in block 25.In some embodiments, UE 120 may utilize antenna switching informationincluded in the assistance data to determine the RSTDs as describedabove. For example, if antenna switching is used on a particular cell,the UE 120 may determine a set of TOA values for each cell, and select afinal TOA from this set for RSTD calculation.

If the assistance data received in block 25 indicates a multi-PRSsequence and frequency shift, the UE 120 may then determine a replicaPRS sequence for TOA estimation by using the seed of equation (3) or (4)accordingly. In some embodiments, ƒ(PAP_(h)) in equation (3) or (4) maybe included in the assistance data received in block 25, together withother OTDOA assistance data such as PCI etc.

Once UE 120 has determined all measurements as requested by the server150 in block 23, such as RSTD measurements for example, it may send themeasurements in an LPP/LPPe Provide Location Information message toserver 150 in block 26. The LPP/LPPe Provide Location Informationmessage in block 26 may include the RSTD measurements together with anidentification of the measured cells, such as the PCI and the ƒ(PAP_(h))for which the RSTDs are provided. In some embodiments, server 150 mayuse the received measurements along with information of the antennalocations from which the UE has performed the measurements as well as BStiming information to calculate the location of UE 120. Server 150 maythen provide the calculated location of UE 120 to LCS client 160, forexample (not shown in FIG. 2D).

In some embodiments, UE 120 may use the measurements together withinformation of the antenna locations from which the UE 120 has performedthe measurements as well as BS timing information to calculate thelocation of UE 120 and possibly report the estimated location to server150. In some embodiments, server 150 may provide the UE locationinformation to LCS client 160.

FIG. 3A shows a traditional single physical transmitting antenna elementsystem 300 with conventional single physical transmitting antennaelement 240 radiating at high power. Conventional single physicaltransmitting antenna element 240 may provide coverage for a singlecell/PCI. Conventional techniques using PRS and OTDOA measurements maybe utilized by UE 120 for location determination in traditional singlephysical transmitting antenna element system 300.

FIG. 3B illustrates DAS 350 with multiple physical transmitting antennaelements 140-1, 140-2, 140-3 and 140-4. In DAS 350, multiple physicaltransmitting antenna elements 140-1, 140-2, 140-3 and 140-4, which maybe spatially separated and connected to a common source may replaceconventional single physical transmitting antenna element 240 andprovide coverage for the same cell. In distributed antenna system 350,the transmitted power is split among physical transmitting antennaelements 140, which may be separated in space so as to provide coverageover the same area as conventional single physical transmitting antennaelement 240, but with reduced total power and improved reliability.Thus, DAS 350 may be realized by replacing traditional single physicaltransmitting antenna element system 300 with a group of low-powerphysical transmitting antenna elements 140-1, 140-2, 140-3 and 140-4 tocover the same area.

In some embodiments, for example as shown in FIG. 3B, where physicaltransmitting antenna elements 140 represent a DAS with antennas 140-1,140-2, 140-3 and 140-4, logical antenna port 6, which is used for PRStransmission, may be mapped to Physical Antenna Ports (PAPs), and a PRSsequence may be generated as a function ƒ(PAP_(h)) of the PhysicalAntenna Port Identifier (PAP ID). In equations (3) and (4) above thefunction of PAP ID is denoted by.

FIG. 4 illustrates an RRH system 400 with multiple RRH transmitters420-1, 420-2 . . . 420-6 serving a single cell. In RRH system 400,individual RRH transmitters 420-1-420-6 may be remote to eNodeB (BS) 410and may be coupled to eNodeB 410 using optical connectors 430. Such asituation may also arise, as described earlier, in LTE-AdvancedCooperative Multi Point (CoMP) transmission, where RRHs provide coveragewithin a macrocell coverage area. In situations where a single or macrocell is served by multiple RRHs or small cells, logical antenna port 6on the RRHs or small cells may be mapped to PAPs, and a PRS sequence maybe generated as a function ƒ(PAP_(h)) of the PAP ID.

In some embodiments, to permit robust position determination of UE 120in DAS 350 (FIG. 3B) or RRH system 400 (FIG. 4), logical antenna port 6,which is used for PRS transmissions, may be mapped to Physical AntennaPorts (PAPs), and a PRS sequence may be generated as a function of thePAP ID. Similarly, in situations where a cell is served by multipleRRHs, logical antenna port 6 on the RRHs may be mapped to PAPs, and aPRS sequence may be generated as a function of the PAP ID.

Accordingly, as discussed earlier, the initialization seed c_(init) maybe modified as shown in equation (3) asc_(init)=2¹⁰·(7·(n_(s)+1)+l+1)·(2·N_(ID) ^(cell)+1)+2·N_(ID)^(cell)+N_(CP)+ƒ(PAP_(h)), or as shown in equation (4) asc_(init)=2¹⁰·(7·(n_(s)+1)+l+1)·(2·(N_(ID)^(cell)+ƒ(PAP_(h)))+1)+2·(N_(ID) ^(cell)+ƒ(PAP_(h)))+N_(CP). Becausec_(init) is a function of the PAP ID PAP_(h), in some embodiments, adifferent PRS sequence may be transmitted from each of physicaltransmitting antenna elements 140-1, 140-2, 140-3 and 140-4 or each RRHdespite sharing a common PCI.

Accordingly, as discussed earlier, the frequency shift may be modifiedas shown in equation (5) above, resulting in a different frequency shiftpattern being transmitted from each of physical transmitting antennaelements 140-1, 140-2, 140-3 and 140-4 or each RRH despite sharing acommon PCI.

FIG. 5A shows a mapping 500 of logical Antenna Port 6 520-6 used for PRStransmission in an antenna switching system to Physical Antenna PortsPAP₀ 530-0 with PAP ID 0 and PAP₁ 530-1 with PAP ID 1. FIG. 5A showslogical antenna ports 520, comprising logical antenna ports 520-1through 520-8 and physical antenna ports 530. In FIG. 5A, logicalantenna port 6 shares the same PCI as eNodeB 510. FIG. 5A assumes thatthere are two physical transmitting antenna elements 140-1 and 140-2 sothat logical antenna port 6 may be mapped to two physical antenna ports0 and 1 shown as PAP0 530-0 and PAP1 530-1, respectively. In FIG. 5A,ƒ(PAP₀) has been defined simply as θ(PAP₀)=0 for PAP₀ with PAP ID 0, andƒ(PAP₁)=1, for PAP₁ with PAP ID 1. Thus, in FIG. 5A, each physicalantenna port 530-0 and 530-1 would transmit a different PRS sequence andfrequency shift, even though they share a common PCI. Note thatƒ(PAP_(h)), as described above, is exemplary and for descriptivepurposes only. In general, ƒ(PAP_(h)) may be set to various mathematicalfunctions of the PAP ID h, such as a linear function, a quadraticfunction, a polynomial, or any other mathematical function which usesthe PAP ID as input value, and provides a defined output valueƒ(PAP_(h)).

In some embodiments, ƒ(PAP_(h)) may be integer numbers, counting thenumber of PAPs of an eNodeB, such as eNodeB 510, e.g., 0, 1, 2, 3, 4, 5for antenna ports 530-0 to 530-5. In another embodiment, ƒ(PAP_(h)) maybe based on, obtained from, or equal to the Cell Portion ID, forexample, as defined in 3GPP Technical Specification 36.455 “LTEPositioning Protocol A (LPPa)”, Release-12.

In some embodiments, the PAP IDs may be provided by server 150 to UE 120as part of the OTDOA assistance data using the appropriate LPP/LPPeprotocols. In some embodiments, the OTDOA assistance data may includePAP IDs, or the function ƒ(PAP_(h)) to allow UE 120 to determine areplica PRS signal for each individual antenna port.

In some embodiments, by mapping logical antenna port 6 to PhysicalAntenna Ports (PAPs), and generating a PRS sequence and frequency shiftas a function of the PAP ID, TX antennas (or RRHs) at different physicallocations may be able to transmit distinct PRS signals despite sharing acommon PCI.

FIG. 5B shows a mapping 550 of logical antenna port 6 520-6 used for PRStransmission in a DAS or RRH system to physical antenna ports PAP0 530-0with PAP ID 0 through PAP5 530-5 with PAP ID 5. FIG. 5B shows logicalantenna ports 520, comprising logical antenna ports 520-1 through 520-8and physical antenna ports 530-0 through 530-5. In FIG. 5B, logicalantenna port 6 shares the same PCI as eNodeB 510. FIG. 5B assumes thatthere are six physical transmitting antenna elements 140-1, 140-2 . . .140-6 at different physical locations. As shown in FIG. 5B, logicalantenna port 6 may be mapped to six physical antenna ports 0 through 5shown as PAP0 530-0 through PAP5 530-5, respectively.

FIG. 6A shows a flowchart for an exemplary method 600 to determine theposition of a UE 120 in a manner consistent with disclosed embodiments.In some embodiments, portions of method 600 may be performed by UE 120,and/or by some combination of UE 120, server 150, and/or another networkentity. The method may start in block 610, for example, when UE 120initiates location determination and/or when LCS client 160 or anothernetwork entity requests location information for UE 120. In someembodiments, portions of method 600 may be performed using an LPP orLLPe protocol.

Next, in block 620, a request for capability information may be receivedby the UE 120. For example, UE 120 may receive a Request Capabilitiesmessage, which may request the capabilities of the UE 120 such as,without limitation, OTDOA capabilities, including capability indicationfor PAPs and/or support for multi-PRS sequences and frequency shiftsfrom the same cell/PCI.

In block 625, UE 120 may determine, based in part, on stored capabilityinformation, whether UE 120 is capable of supporting/receiving OTDOAassistance information pertaining to PAPs, multi-PRS sequences andfrequency shifts from the same cell/PCI, and/or antenna switchingassistance data. For example, the antenna switching assistanceinformation may include PRS assistance information for one or morecells, which may comprise Boolean parameters corresponding to the one ormore cells. Each Boolean parameter may indicate whether antennaswitching occurs between PRS positioning occasions for a correspondingcell. In some embodiments, the antenna switching assistance informationmay also include information pertaining to an antenna switchinginterval. The antenna switching interval may be specified in terms ofthe number of consecutive PRS positioning occasions transmitted on aphysical transmitting antenna element in the at least one cell beforethe physical transmitting antenna element is switched.

If UE 120 determines that it is capable of supporting OTDOA assistanceinformation pertaining to PAPs, multi-PRS sequences and frequency shiftsfrom the same cell/PCI, and/or antenna switching assistance data (“Y” inblock 630) then, in block 630, UE 120 may receive all of the assistanceinformation requested by the UE 120, which may include the OTDOAassistance data defined in LPP and/or LPPe and may also includeassistance information pertaining to multi-PRS sequences and frequencyshifts from the same cell/PCI, antenna switching assistance data, and/orPAP assistance information.

In block 635, UE 120 may measure RSTDs between a reference cell andmultiple neighbor cells based on the OTDOA assistance data. In someembodiments, UE 120 may utilize the antenna switching informationincluded in the assistance data to determine the RSTDs as describedabove. In one embodiment, if antenna switching is used on a particularcell, UE 120 may determine a set of TOA values for each cell, and selectone TOA from this set for RSTD calculation. For example, if antennaswitching is used by the at least one cell, then, UE 120 may select aTime of Arrival value for a PRS from a set of TOA values determinedbased on PRS related measurements at the UE during a single PRSpositioning occasion. In some embodiments, the selected TOA value may beindicative of a shorter distance between a source of the PRS and the UE120 than the other TOA values in the set.

If UE 120 determines that it is not capable of supporting OTDOAassistance information pertaining to PAPs, multi-PRS sequences andfrequency shifts from the same cell/PCI, and/or antenna switchingassistance data etc. (“N” in block 630) then, in block 650, in someembodiments, UE 120 may receive legacy assistance information. Forexample, in some embodiments, UE 120 may receive information pertainingto a physical transmitting antenna element that maintains a PRS sequenceunmodified by ƒ(PAP_(h)), which may be achieved by setting ƒ(PAP)=0. Forexample, UE 120 may be provided with information pertaining to physicalantenna port PAP₀, for which ƒ(PAP)=0. Next, in block 655, UE 120 maymeasure RSTDs based on the legacy assistance information received inblock 650.

In some embodiments, the position of UE 120 may then be determined inblock 640 using the measured RSTD information. In some embodiments, UE120 may compute its own location. In another embodiment, the position ofUE 120 may be computed by server 150 based on the measured RSTDinformation. The method may terminate in block 660. Method 600 isexemplary and various modifications may be made by combining or omittingblocks as would be apparent to one of ordinary skill in the art. Forexample, in some embodiments, such as where no legacy support isprovided, blocks 650 and 655 may be omitted and the method may proceedto block 660, where it terminates. As another example, the method may bemodified depending on the protocol used for location assistance, thecapabilities of UE 120, and/or capabilities of served 50.

FIG. 6B shows a flowchart for another exemplary method 675 to determinethe position of a UE 120 in a manner consistent with disclosedembodiments. In some embodiments, portions of method 675 may beperformed by UE 120. The method may start in block 680, for example,when UE 120 initiates location determination and/or when LCS client 160or another network entity requests location information for UE 120. Insome embodiments, portions of method 675 may be performed using an LPPor LLPe protocol.

Next, in block 630, DE 120 may receive all of the assistance informationrequested by the UE 120, which may include the OTDOA assistance datadefined in LPP and/or LPPe and may also include assistance informationpertaining to multi-PRS sequences and frequency shifts from the samecell/PCI, antenna switching assistance data, and/or PAP assistanceinformation. For example, UE 120 may receive the OTDOA assistanceinformation, which may comprise Positioning Reference Signal (PRS)assistance information including antenna switching assistanceinformation for a cell.

In block 685, UE 120 may determine whether physical transmitting antennaelement switching is used by the cell based, at least in part, on thereceived antenna switching assistance information.

Next, in block 690, if physical transmitting antenna element switchingis used by the cell, then, UE 120 may select a Time of Arrival (TOA)value for a PRS from a set of TOA values determined based onmeasurements at the UE during a single PRS positioning occasion, wherethe PRS is received by the UE and the selected TOA value is indicativeof a shorter distance between a source of the PRS and the UE than otherTOA values in the set of TOA values. In some embodiments, the selectedTOA value may be used to determine an estimated location of UE 120. Themethod may terminate in block 660.

FIG. 7A shows a flowchart for an exemplary method 700 to determine theposition of UE 120 in a manner consistent with disclosed embodiments. Insome embodiments, portions of method 700 may be performed by a server150. The method may start in block 710, for example, when server 150 orUE 120 initiates location determination and/or when LCS client 160 oranother network entity requests location information for UE 120. In someembodiments, portions of method 700 may be performed using an LPP orLLPe protocol.

Next, in block 715, server 150 may receive capability information fromUE 120. In some embodiments, the capability information may be receivedin a Provide Capabilities message, in response to an earlier RequestCapabilities message sent by server 150. In some embodiments, thecapability information received by server 150 may include, withoutlimitation, information pertaining to mobile station's OTDOAcapabilities, including an indication of support for PAPs, antennaswitching assistance information, and/or support for multi-PRS sequencesand frequency shifts from the same cell/PCI.

In block 720, server 150 may determine, based in part, on the receivedcapability information, whether UE 120 is capable ofsupporting/receiving OTDOA assistance information pertaining to PAPs,multi-PRS sequences and frequency shifts from the same cell/PCI, and/orantenna switching assistance data.

If server 150 determines that UE 120 is capable of supporting OTDOAassistance information pertaining to PAPs, multi-PRS sequences andfrequency shifts from the same cell/PCI, and/or antenna switchingassistance data (“Y” in block 720) then, in block 725, server 150 maysend all of the assistance information requested by UE 120, which mayinclude the OTDOA assistance data defined in LPP and/or LPPe and mayalso include assistance information pertaining to multi-PRS sequencesand frequency shifts from the same cell/PCI, antenna switchingassistance data, and/or PAP assistance information. In some embodiments,server 150 may transmit the PAP ID as part of OTDOA assistanceinformation. Further, the PAP ID may be transmitted as part of OTDOAassistance information based, in part, on received informationindicating a capability to generate a replica PRS sequence at UE 120 incommunication with server 150 (e.g. a location server). In someembodiments, the location assistance information may be transmitted in aProvide Assistance Data message to UE 120.

If server 150 determines that UE 120 does not support OTDOA assistanceinformation pertaining to PAPs, multi-PRS sequences and frequency shiftsfrom the same cell/PCI, and/or antenna switching assistance data (“N” inblock 720) then, in block 740, in some embodiments, server 150 may sendlegacy assistance information to UE 120. For example, in someembodiments, server 150 may send information pertaining to a physicaltransmitting antenna element that maintains a PRS sequence unmodified byƒ(PAP_(h)), which may be achieved by setting ƒ(PAP)=0. For example,server 150 may send information pertaining to physical antenna portPAP₀, for which ƒ(PAP)=0.

Next, in block 730, server 150 may receive RSTDs measured by UE 120based on the provided assistance information. In block 735, the locationof UE 120 may be determined based on the measured RSTDs. For example, ifantenna switching is used on a particular cell, server 150 may receiveone TOA value from a set of measured TOA based on the OTDOA assistanceinformation provided.

In some embodiments, the position of UE 120 may then be determined inblock 735 using the measured RSTD information. In some embodiments, UE120 may compute its own location and relay the location to server 150.In another embodiment, the position of UE 120 may be computed by server150 based on the measured RSTD information. The method may thenterminate in block 750.

Method 700 is exemplary and various modifications may be made bycombining or omitting blocks as would be apparent to one of ordinaryskill in the art. For example, in some embodiments, such as where nolegacy support is provided, block 740 may be omitted and the method mayproceed to block 750, where it terminates. As another example, themethod may be modified depending on the protocol used for locationassistance, the capabilities of UE 120, and/or capabilities of thelocation assistance server.

FIG. 7B shows a flowchart for an exemplary method 755 that may be usedduring location estimation in a manner consistent with disclosedembodiments. In some embodiments, portions of method 755 may beperformed by a server 150. The method may start in block 757, forexample, when server 150 or UE 120 initiates location determinationand/or when LCS client 160 or another network entity requests locationinformation for UE 120. In some embodiments, portions of method 755 maybe performed using an LPP or LLPe protocol.

Next, in block 725, server 150 may send all of the assistanceinformation requested by UE 120, which may include the OTDOA assistancedata defined in LPP and/or LPPe and may also include assistanceinformation pertaining to multi-PRS sequences and frequency shifts fromthe same cell/PCI, antenna switching assistance data, and/or PAPassistance information. For example, server 150 may send OTDOAassistance information to UE 120, where the OTDOA assistance informationmay comprise Positioning Reference Signal (PRS) assistance informationincluding antenna switching assistance information for at least one cellin a subset of cells served by the server 150. The term “subset” as usedherein, refers to one or more elements of a set. In some instances thesubset may comprise a plurality of elements of a set. In some instances,a subset may include all of the elements of a set. The method may thenterminate in block 759.

FIG. 7C shows an exemplary method 760 of generating distinct PRSsequences and frequency shifts in a system comprising a plurality ofphysical transmitting antenna elements. In some embodiments, portions ofmethod 760 may be performed by an entity within system 100 to determinea particular radio network configuration. The method may start in block762, for example, when the radio network is being set-up, planned,configured, or re-configured.

Next, in block 765, system 100 and/or an entity in system 100 may assigna distinct PAP ID to a subset of the plurality of physical transmittingantenna elements.

In block 770, the radio network may generate PRS sequences for thesubset of the plurality of physical transmitting antenna elements, whereeach PRS sequence corresponds to a physical transmitting antenna elementin the subset of the plurality of physical transmitting antennaelements, and a function ƒ(PAP_(h)) is added to a seed for a length-31Gold sequence used to generate a PRS sequence for a correspondingphysical transmitting antenna element, the function ƒ(PAP_(h)) beingbased on the PAP ID (h) of the corresponding physical transmittingantenna element.

In block 775, the radio network may apply, to each generated PRSsequence (e.g. in block 765) corresponding to a physical transmittingantenna element in the subset, a corresponding frequency shift based, atleast in part, on: (i) the PAP ID (h), or (ii) the function ƒ(PAPh), or(iii) some combination thereof, of the corresponding physicaltransmitting antenna element.

In some embodiments, blocks 770 and 775 may be combined so that theradio network may generate PRS sequences and frequency shifts for thesubset of the plurality of physical transmitting antenna elements, whereeach PRS sequence and frequency shift corresponds to a physicaltransmitting antenna element in the subset of the plurality of physicaltransmitting antenna elements, and a function ƒ(PAP_(h)) is added to aseed for a length-31 Gold sequence used to generate a PRS sequence for acorresponding physical transmitting antenna element, and a functionƒ(PAP_(h)) may be added to the formula for generating the PRS patternfrequency shift, where the function ƒ(PAP_(h)) being based on the PAP ID(h) of the corresponding physical transmitting antenna element. Themethod may terminate in block 780.

FIG. 7D shows an exemplary method 785 of generating distinct PRSsequences with frequency shifts in a system comprising a plurality ofphysical transmitting antenna elements, which may serve a single cell.In some embodiments, portions of method 785 may be performed by anentity within system 100 to determine a particular radio networkconfiguration. The method may start in block 710, for example, when theradio network is being set-up, planned, configured, or re-configured.

Next, in block 789, system 100 and/or an entity in system 100 may assigna distinct PAP ID to each physical transmitting antenna element in theplurality of physical transmitting antenna element.

In block 791, the radio network may generate plurality of PRS sequences,where each PRS sequence in the plurality of PRS sequences corresponds toa distinct physical transmitting antenna element in the plurality ofphysical transmitting antenna elements, and wherein each PRS sequencehas a corresponding frequency shift based, at least in part, on acorresponding PAP ID (h) of a corresponding physical transmittingantenna element.

In some embodiments, the frequency shift may be based on a functionƒ(PAP_(h)) obtained from the PAP ID (h) of the corresponding physicaltransmitting antenna element. In some embodiments, ƒ(PAP_(h)) may be setto 0 for at least one of the plurality of physical transmitting antennaelements in the subset of the plurality of physical transmitting antennaelements. Further, in some embodiments, ƒ(PAP_(h)) may be based on aCell Portion ID, wherein the Cell Portion ID comprises an identifierassociated with a geographic portion of a cell.

In some embodiments, the plurality of physical transmitting antennaelements may comprise a Distributed Antenna System (DAS). In someembodiments, the plurality of physical transmitting antenna elements maybe realized using Remote Radio Heads (RRHs). In some embodiments, theplurality of physical transmitting antenna elements comprise a smallcell, such as, but not limited to, a femtocell.

In some embodiments, the PAP ID and/or ƒ(PAP_(h)) may be transmitted aspart of Observed Time Difference of Arrival (OTDOA) assistanceinformation. In some instances, transmission of the PAP ID and/orƒ(PAP_(h)) as OTDOA assistance data may be based, at least in part, onreceived information indicating a capability to receive the OTDOAassistance data at a mobile station. The method may terminate in block780.

FIG. 8 shows a schematic block diagram illustrating certain exemplaryfeatures of UE 120 enabled to support OTDOA measurement using PRSassistance information in systems with antenna diversity, DAS, and/orRRHs or small cells in a manner consistent with disclosed embodiments.UE 120 may, for example, include one or more processing units 302,memory 304, a transceiver 310 (e.g., wireless network interface), and(as applicable) an SPS receiver 340, which may be operatively coupledwith one or more connections 306 (e.g., buses, lines, fibers, links,etc.) to non-transitory computer-readable medium 320 and memory 304. Incertain example implementations, all or part of UE 120 may take the formof a chipset, and/or the like. The SPS receiver 340 may be enabled toreceive signals associated with one or more SPS resources. Transceiver310 may, for example, include a transmitter 312 enabled to transmit oneor more signals over one or more types of wireless communicationnetworks and a receiver 314 to receive one or more signals transmittedover the one or more types of wireless communication networks.

Processing unit 302 may be implemented using a combination of hardware,firmware, and software. In some embodiments, processing unit 302 mayinclude UE PRS Assistance Data Module 316, which may process receivedOTDOA assistance information, including PRS assistance information. Forexample, UE PRS Assistance Data Module 316 may process PRS assistanceinformation comprising antenna switching assistance informationincluding antenna switching pattern information and antenna mutinginformation. In some embodiments, UE PRS Assistance Data Module 316 mayalso process PAP IDs, and/or the function ƒ(PAP_(h)) received as part ofOTDOA assistance information. Processing unit 302 may also be capable ofprocessing various other received LPP/LPPe messages including assistanceinformation either directly or in conjunction with one or more otherfunctional blocks shown in FIG. 8. In some embodiments, processing unit302 may represent one or more circuits configurable to perform at leasta portion of a data signal computing procedure or process related to theoperation of UE 120.

In some embodiments, UE 120 may include one or more UE antennas (notshown) which may be internal or external. UE antennas may be used totransmit and/or receive signals processed by transceiver 310 and/or SPSreceiver 340. In some embodiments, UE antennas may be coupled totransceiver 310 and SPS receiver 340. In some embodiments, measurementsof signals received (transmitted) by UE 120 may be performed at thepoint of connection of the UE antennas and transceiver 310. For example,the measurement point of reference for received (transmitted) RF signalmeasurements may be an input (output) terminal of the receiver 314(transmitter 312) and an output (input) terminal of the UE antennas. Inan UE 120 with multiple UE antennas or antenna arrays, the antennaconnector may be viewed as a virtual point representing the aggregateoutput (input) of multiple UE antennas. In some embodiments, UE 120 maymeasure received signals including signal strength and TOA measurementsand the raw measurements may be processed by processing units 302.

The methodologies described herein may be implemented by various meansdepending upon the application. For example, these methodologies may beimplemented in hardware, firmware, software, or any combination thereof.For a hardware implementation, the processing unit 302 may beimplemented within one or more application specific integrated circuits(ASICs), digital signal processors (DSPs), digital signal processingdevices (DSPDs), programmable logic devices (PLDs), field programmablegate arrays (FPGAs), processors, controllers, micro-controllers,microprocessors, electronic devices, other electronic units designed toperform the functions described herein, or a combination thereof.

For a firmware and/or software implementation, the methodologies may beimplemented with modules (e.g., procedures, functions, and so on) thatperform the functions described herein. Any machine-readable mediumtangibly embodying instructions may be used in implementing themethodologies described herein. For example, software codes may bestored in a non-transitory computer-readable medium 320 or memory 304that is connected to and executed by processing unit 302. Memory may beimplemented within the processor unit or external to the processor unit.As used herein the term “memory” refers to any type of long term, shortterm, volatile, nonvolatile, or other memory and is not to be limited toany particular type of memory or number of memories, or type of mediaupon which memory is stored.

If implemented in firmware and/or software, the functions may be storedas one or more instructions or program code 308 on a non-transitorycomputer-readable medium, such as medium 320 and/or memory 304. Examplesinclude computer-readable media encoded with a data structure andcomputer-readable media encoded with a computer program. For example,the non-transitory computer-readable medium including program code 308stored thereon may include program code 308 to support OTDOA measurementusing PRS assistance information in systems with antenna diversity, DAS,and/or RRHs in a manner consistent with disclosed embodiments.Non-transitory computer-readable media includes physical computerstorage media. A storage medium may be any available medium that can beaccessed by a computer. By way of example, and not limitation, suchnon-transitory computer-readable media can comprise RAM, ROM, EEPROM,CD-ROM or other optical disk storage, magnetic disk storage or othermagnetic storage devices, or any other medium that can be used to storedesired program code 308 in the form of instructions or data structuresand that can be accessed by a computer; disk and disc, as used herein,includes compact disc (CD), laser disc, optical disc, digital versatiledisc (DVD), floppy disk and blu-ray disc where disks usually reproducedata magnetically, while discs reproduce data optically with lasers.Combinations of the above should also be included within the scope ofcomputer-readable media.

In addition to storage on computer readable medium 320, instructionsand/or data may be provided as signals on transmission media included ina communication apparatus. For example, a communication apparatus mayinclude a transceiver 310 having signals indicative of instructions anddata. The instructions and data are configured to cause one or moreprocessors to implement the functions outlined in the claims. That is,the communication apparatus includes transmission media with signalsindicative of information to perform disclosed functions.

Memory 304 may represent any data storage mechanism. Memory 304 mayinclude, for example, a primary memory and/or a secondary memory.Primary memory may include, for example, a random access memory, readonly memory, etc. While illustrated in this example as being separatefrom processing unit 302, it should be understood that all or part of aprimary memory may be provided within or otherwise co-located/coupledwith processing unit 302. Secondary memory may include, for example, thesame or similar type of memory as primary memory and/or one or more datastorage devices or systems, such as, for example, a disk drive, anoptical disc drive, a tape drive, a solid state memory drive, etc.

In certain implementations, secondary memory may be operativelyreceptive of, or otherwise configurable to couple to a non-transitorycomputer-readable medium 320. As such, in certain exampleimplementations, the methods and/or apparatuses presented herein maytake the form in whole or part of a computer-readable medium 320 thatmay include computer implementable instructions 308 stored thereon,which if executed by at least one processing unit 302 may be operativelyenabled to perform all or portions of the example operations asdescribed herein. Computer readable medium 320 may be a part of memory304.

Reference is now made to FIG. 9, which is a schematic block diagramillustrating a server 150 enabled to support OTDOA measurement using PRSassistance information in systems with antenna diversity, DAS, and/orRRHs or small cells in a manner consistent with disclosed embodiments.In some embodiments, server 150 may include, for example, one or moreprocessing units 352, memory 354, storage 360, and (as applicable)communications interface 390 (e.g., wireline or wireless networkinterface), which may be operatively coupled with one or moreconnections 356 (e.g., buses, lines, fibers, links, etc.). In certainexample implementations, some portion of server 150 may take the form ofa chipset, and/or the like.

Communications interface 390 may include a variety of wired and wirelessconnections that support wired transmission and/or reception and, ifdesired, may additionally or alternatively support transmission andreception of one or more signals over one or more types of wirelesscommunication networks. Communications interface 390 may also includeinterfaces for communication with various other computers andperipherals. For example, in one embodiment, Communications interface390 may comprise network interface cards, input-output cards, chipsand/or ASICs that implement one or more of the communication functionsperformed by server 150. In some embodiments, communications interface390 may also interface with network 130 to obtain a variety of networkconfiguration related information, such as PCIs, configured PRSinformation, and/or timing information used by the base stations in thenetwork. For example, Communications interface 390 may make use of the“LTE Positioning Protocol A (LPPa)” defined in 3GPP TS 36.455 or amodification of this protocol to obtain PCI, configured PRS, timingand/or other information from the base stations in network 130.Processing unit 352 may use some or all of the received information togenerate OTDOA assistance data information in a manner consistent withdisclosed embodiments.

Processing unit 352 may be implemented using a combination of hardware,firmware, and software. In some embodiments, processing unit 352 mayinclude Server PRS Assistance Data Module 366, which may generate OTDOAinformation, including PRS assistance information for transmission to UE120. For example, Server PRS Assistance Data Module 366 may generateand/or format PRS assistance information comprising antenna switchingassistance information and antenna switching pattern information. Insome embodiments, Server PRS Assistance Data Module 366 may alsogenerate PAP IDs, or the function ƒ(PAP_(h)) as part of OTDOA assistanceinformation for transmission to UE 120. Processing unit 352 may also becapable of processing various other LPP/LPPe assistance informationeither directly or in conjunction with one or more other functionalblocks shown in FIG. 9. In some embodiments, processing unit 352 maygenerate the OTDOA assistance information as Long Term Evolution (LTE)Positioning Protocol (LPP) or LPP extensions (LPPe) messages. In someembodiments, processing unit 352 may represent one or more circuitsconfigurable to perform at least a portion of a data signal computingprocedure or process related to the operation of server 150.

The methodologies described herein in flow charts and message flows maybe implemented by various means depending upon the application. Forexample, these methodologies may be implemented in hardware, firmware,software, or any combination thereof. For a hardware implementation, theprocessing unit 352 may be implemented within one or more applicationspecific integrated circuits (ASICs), digital signal processors (DSPs),digital signal processing devices (DSPDs), programmable logic devices(PLDs), field programmable gate arrays (FPGAs), processors, controllers,micro-controllers, microprocessors, electronic devices, other electronicunits designed to perform the functions described herein, or acombination thereof.

For a firmware and/or software implementation, the methodologies may beimplemented with modules (e.g., procedures, functions, and so on) thatperform the functions described herein. Any machine-readable mediumtangibly embodying instructions may be used in implementing themethodologies described herein. For example, software may be stored inremovable media drive 370, which may support the use of non-transitorycomputer-readable media 358, including removable media. Program code maybe resident on non-transitory computer readable media 358 or memory 354and may be read and executed by processing units 352. Memory may beimplemented within processing units 352 or external to the Processingunits 352. As used herein the term “memory” refers to any type of longterm, short term, volatile, nonvolatile, or other memory and is not tobe limited to any particular type of memory or number of memories, ortype of media upon which memory is stored.

If implemented in firmware and/or software, the functions may be storedas one or more instructions or code on a non-transitorycomputer-readable medium 358 and/or memory 354. Examples includecomputer-readable media encoded with a data structure andcomputer-readable media encoded with a computer program. For example,non-transitory computer-readable medium 358 including program codestored thereon may include program code to support OTDOA measurementusing PRS assistance information in systems with antenna diversity, DAS,and/or RRHs or small cells in a manner consistent with disclosedembodiments.

Non-transitory computer-readable media includes a variety of physicalcomputer storage media. A storage medium may be any available mediumthat can be accessed by a computer. By way of example, and notlimitation, such non-transitory computer-readable media can compriseRAM, ROM, EEPROM, CD-ROM or other optical disk storage, magnetic diskstorage or other magnetic storage devices, or any other medium that canbe used to store desired program code in the form of instructions ordata structures and that can be accessed by a computer; disk and disc,as used herein, includes compact disc (CD), laser disc, optical disc,digital versatile disc (DVD), floppy disk and blu-ray disc where disksusually reproduce data magnetically, while discs reproduce dataoptically with lasers. Other embodiments of non-transitory computerreadable media include flash drives, USB drives, solid state drives,memory cards, etc. Combinations of the above should also be includedwithin the scope of computer-readable media.

In addition to storage on computer readable medium, instructions and/ordata may be provided as signals on transmission media to communicationsinterface 390, which may store the instructions/data in memory 354,storage 360 and/or relayed the instructions/data to processing units 352for execution. For example, communications interface 390 may receivewireless or network signals indicative of instructions and data. Theinstructions and data are configured to cause one or more processors toimplement the functions outlined in the claims. That is, thecommunication apparatus includes transmission media with signalsindicative of information to perform disclosed functions.

Memory 354 may represent any data storage mechanism. Memory 354 mayinclude, for example, a primary memory and/or a secondary memory.Primary memory may include, for example, a random access memory, readonly memory, nonvolatile RAM, etc. While illustrated in this example asbeing separate from processing unit 352, it should be understood thatall or part of a primary memory may be provided within or otherwiseco-located/coupled with processing unit 352. Secondary memory mayinclude, for example, the same or similar type of memory as primarymemory and/or storage 360 such as one or more data storage devicesincluding, for example, hard disk drives, optical disc drives, tapedrives, a solid state memory drive, etc. In some embodiments, storage360 may comprise one or more databases that may hold informationpertaining to various entities in system 100 and/or the broader cellularnetwork. In some embodiments, information in the databases may be read,used and/or updated by processing units 352 during various computations,including storing capabilities of MS120, capabilities of server 150,generating OTDOA assistance data, computing a location of UE 120, etc.

In certain implementations, secondary memory may be operativelyreceptive of, or otherwise configurable to couple to a non-transitorycomputer-readable medium 358. As such, in certain exampleimplementations, the methods and/or apparatuses presented herein maytake the form in whole or part of a removable media drive 370 that mayinclude non-transitory computer readable medium 358 with computerimplementable instructions stored thereon, which if executed by at leastone processing unit 352 may be operatively enabled to perform all orportions of the example operations as described herein. Computerreadable medium 358 may be a part of memory 354.

Although the present description is illustrated in connection withspecific embodiments for instructional purposes, claimed subject matteris not necessarily limited thereto. Various adaptations andmodifications may be made without departing from the scope of thedescription.

What is claimed is:
 1. A processor-implemented method of generating aPositioning Reference Signal (PRS) sequence, the method comprising:assigning a distinct Physical Antenna Port (PAP) identifier (ID) to eachphysical transmitting antenna element in a plurality of physicaltransmitting antenna elements serving a single cell; and generating aplurality of PRS sequences, each PRS sequence in the plurality of PRSsequences corresponding to a distinct physical transmitting antennaelement in the plurality of physical transmitting antenna elements,wherein each PRS sequence has a corresponding frequency shift based, atleast in part, on a corresponding PAP ID (h) of a corresponding physicaltransmitting antenna element.
 2. The method of claim 1, wherein thecorresponding frequency shift is based on a corresponding functionƒ(PAP_(h)) of the corresponding PAP ID (h) of the corresponding physicaltransmitting antenna element.
 3. The method of claim 2, whereingenerating a plurality of PRS sequences comprises: setting, for one ofthe plurality of physical transmitting antenna elements, thecorresponding function ƒ(PAP_(h)) to
 0. 4. The method of claim 2,wherein the corresponding function ƒ(PAP_(h)) is based further on a CellPortion ID, wherein the Cell Portion ID comprises an identifierassociated with a geographic portion of the single cell.
 5. The methodof claim 1, wherein the plurality of physical transmitting antennaelements comprise one of: a Distributed Antenna System (DAS), or smallcells.
 6. The method of claim 1, wherein the plurality of physicaltransmitting antenna elements are realized using Remote Radio Heads(RRHs).
 7. The method of claim 1, further comprising: initiatingtransmission of Observed Time Difference of Arrival (OTDOA) assistanceinformation for one or more physical transmitting antenna elements ofthe plurality of physical transmitting antenna elements, wherein, OTDOAassistance information for a physical transmitting antenna element inthe one or more physical transmitting antenna elements comprises acorresponding PAP ID (h).
 8. The method of claim 7, wherein initiatingtransmission of the OTDOA assistance information comprises: initiatingtransmission of the OTDOA assistance information to a User Equipment(UE), in response to received information from the UE indicating acapability to receive the OTDOA assistance information comprising thecorresponding PAP ID (h).
 9. An apparatus comprising: a transceiver, thetransceiver capable of transmitting Positioning Reference Signal (PRS)information; and a processor coupled to the transceiver, the processorconfigured to: assign a distinct Physical Antenna Port (PAP) identifier(ID) to each physical transmitting antenna element in a plurality ofphysical transmitting antenna elements serving a single cell; andgenerate a plurality of PRS sequences, each PRS sequence in theplurality of PRS sequences corresponding to a distinct physicaltransmitting antenna element in the plurality of physical transmittingantenna elements, wherein each PRS sequence has a correspondingfrequency shift based, at least in part, on a corresponding PAP ID (h)of a corresponding physical transmitting antenna element.
 10. Theapparatus of claim 9, wherein the corresponding frequency shift is basedon a corresponding function ƒ(PAP_(h)) of the corresponding PAP ID (h)of the corresponding physical transmitting antenna element.
 11. Theapparatus of claim 10, to generate a plurality of PRS sequences, theprocessor is configured to: set, for one of the plurality of physicaltransmitting antenna elements, the corresponding function ƒ(PAP_(h)) to0.
 12. The apparatus of claim 10, wherein the corresponding functionƒ(PAP_(h)) is based further on a Cell Portion ID, wherein the CellPortion ID comprises an identifier associated with a geographic portionof the single cell.
 13. The apparatus of claim 9, wherein the pluralityof physical transmitting antenna elements comprise one of: a DistributedAntenna System (DAS), or small cells.
 14. The apparatus of claim 9,wherein the plurality of physical transmitting antenna elements arerealized using Remote Radio Heads (RRHs).
 15. The apparatus of claim 9,wherein the processor is further configured to: initiate transmission ofthe PAP ID (h) as part of Observed Time Difference of Arrival (OTDOA)assistance information for the corresponding physical transmittingantenna element.
 16. The apparatus of claim 15, wherein to initiatetransmission of the OTDOA assistance information, the processor isconfigured to: intitiate transmission of the OTDOA assistanceinformation to a User Equipment (UE), in response to receivedinformation from the UE indicating a capability to receive the OTDOAassistance information comprising the corresponding PAP ID (h).
 17. Aapparatus comprising: transceiver means capable of transmittingPositioning Reference Signal (PRS) information; and processing means,the processing means comprising: means for assigning a distinct PhysicalAntenna Port (PAP) identifier (ID) to each physical transmitting antennaelement in a plurality of physical transmitting antenna elements servinga single cell; and means for generating a plurality of PRS sequences,each PRS sequence in the plurality of PRS sequences corresponding to adistinct physical transmitting antenna element in the plurality ofphysical transmitting antenna elements, wherein each PRS sequence has acorresponding frequency shift based, at least in part, on acorresponding PAP ID (h) of a corresponding physical transmittingantenna element.
 18. The apparatus of claim 17, wherein thecorresponding frequency shift is based on a corresponding functionƒ(PAP_(h)) of the corresponding PAP ID (h) of the corresponding physicaltransmitting antenna element.
 19. The apparatus of claim 18, whereinmeans for generating comprises: means for setting, for one of theplurality of physical transmitting antenna elements, the correspondingfunction ƒ(PAP_(h)) to
 0. 20. The apparatus of claim 18, wherein thecorresponding function ƒ(PAP_(h)) is based further on a Cell Portion ID,wherein the Cell Portion ID comprises an identifier associated with ageographic portion of the single cell.
 21. The apparatus of claim 17,wherein the plurality of physical transmitting antenna elements compriseone of: a Distributed Antenna System (DAS), or small cells.
 22. Theapparatus of claim 17, wherein the plurality of physical transmittingantenna elements are realized using Remote Radio Heads (RRHs).
 23. Theapparatus of claim 17, further comprising: means for initiatingtransmission of Observed Time Difference of Arrival (OTDOA) assistanceinformation for one or more physical transmitting antenna elements ofthe plurality of physical transmitting antenna elements, wherein, OTDOAassistance information for a physical transmitting antenna element inthe one or more physical transmitting antenna elements comprises acorresponding PAP ID (h).
 24. An article comprising: a non-transitorycomputer readable medium comprising instructions to that are executableby a processor to: assign a distinct Physical Antenna Port (PAP)identifier (ID) to each physical transmitting antenna element in aplurality of physical transmitting antenna elements serving a singlecell; and generate a plurality of Positioning Reference Signal (PRS)sequences, each PRS sequence in the plurality of PRS sequencescorresponding to a distinct physical transmitting antenna element in theplurality of physical transmitting antenna elements, wherein each PRSsequence has a corresponding frequency shift based, at least in part, ona corresponding PAP ID (h) of a corresponding physical transmittingantenna element.
 25. The article of claim 24, wherein the correspondingfrequency shift is based on a corresponding function ƒ(PAP_(h)) of thecorresponding PAP ID (h) of the corresponding physical transmittingantenna element.
 26. The article of claim 25, wherein the instructionsto generate a plurality of PRS sequences comprise instructions to: set,for one of the plurality of physical transmitting antenna elements, thecorresponding function ƒ(PAP_(h)) to
 0. 27. The article of claim 25,wherein the corresponding function ƒ(PAP_(h)) is based further on a CellPortion ID, wherein the Cell Portion ID comprises an identifierassociated with a geographic portion of the single cell.
 28. The articleof claim 24, wherein the plurality of physical transmitting antennaelements comprise one of: a Distributed Antenna System (DAS); or smallcells.
 29. The article of claim 24, wherein the plurality of physicaltransmitting antenna elements are realized using Remote Radio Heads(RRHs).
 30. The article of claim 24, wherein the instructions that areexecutable by the processor further comprise instructions to: initiatetransmission of Observed Time Difference of Arrival (OTDOA) assistanceinformation for one or more physical transmitting antenna elements ofthe plurality of physical transmitting antenna elements, wherein, OTDOAassistance information for a physical transmitting antenna element inthe one or more physical transmitting antenna elements comprises acorresponding PAP ID (h).